Outlook 2010 SP2Mailbox on Exchange 2016Shared mailbox on Exchange 2010Outlook takes approx. 1 minute to open after which mailbox performs as it should.

Looking at connection status (ctrl+right click) while Outlook is taking 1 minute to open, it appears Outlook is trying to open the shared mailbox on Exchange 2010 using RPC/HTTP (Outlook Anywhere). This fails and then falls back to RPC/TCP and Outlook opens and works as it should.

With fiddler open I can see Outlook hitting /rpc/rpcproxy.dll?<cas array dns name>. The DNS for the Exchange 2010 cas array points to the Exchange 2010 Client Access Server.

5 Replies

Have you followed Microsoft Exchange Server Deployment Assistant ?Once you introduce a new Exchange version into the environment you need to point all client access to it. There couple of possible scenarios here.Given SCP points to Exchange 2016, it will either proxy or redirect connections to mailboxes on Exchange 2010. That would depend if there's a separate FQDN for Exchange 2016 and Exchange 2010 and if ExternalURL is defined in Exchange 2010 virtual directories that specifically points to the older Exchange version.In order to assist with your issue further, please post results of: (mask the real FQDNs as well as paste the results in Powershell format using the "Insert code" button.)

I think Lucid’s suggestion should work for you. There is no doubt that using Exchange server deployment assistant will very handy for you as it provides step-wise instructions by checking all necessary prerequisites.

You can also use solution like Lepide Exchange migrator to migrate mailboxes. You can migrate everything with this. Pre migration analysis and migration scheduling features will make your job lot easier.

Where cas.domain.com and cas1.domain.com are pointing to? It's should be either two A records in DNS or load-balancer's IP FQDN which sends traffic to servers. In case of A records, which servers they're pointing to? In case of load-balancer - which servers are being load-balanced?

According to the output, highly-likely that the slowness is cased because of outlook.domain.com is pointing to multiple servers. This causes slowness since the discovery process of the relevant mailbox is being bounced between the servers.

The solution would be:1. Point outlook.domain.com to Exchange 2016, with DAG IP or A record in DNS which resolves to either Exchange 2016 servers.2. Adjust URLs for the Exchange 2010 environment to have Exchange 2016 proxy access to mailbox servers.3. If there are no mailboxes on Exchange 2010 CAS servers, they can be safely removed.

Thanks for your reply, I should have added some additional commentary to the output of the PowerShell queries. The reason I didn't is because I didn't want to influence the replies.

We are in the middle of a Datacentre migration from 4 data centres to 2. Rather than trying to copy databases to the 2 new datacentres we took the opportunity to upgrade to Exchange 2016 and do mailbox migrations to get the mailboxes to the new site. This way we can have full control on when and who gets moved to the new datacentre. This will also enhance/simplify our ability to ustilise Exchange Online for archiving only.

Basically, we have 4 AD sites (also different datacentres).

Site 1: Exchange 2010 (separate MBX, CAS and HT). MBX server is in a cross-site DAG with multi-role server in site2.

Site 2: Exchange 2010 (multi-role server MBX/CAS/HT) - in a DAG with site 1 mbx server. Site 2 also has another MBX ( Exchange 2010 SP3 latest RU) server which is in a DAG with the mbx server in Site 3. Database copies on both DAGS are never activated, only in DR testing or real DR. Site 2 is basically our DR site.

Site 3: Exchange 2010 (MBX server and HT/CAS server). MBX server is in a DAG with Site 2 MBX server. All the mailboxes on this server have been migrated to site 4 (EXH 2016).

outlook.domain.com points to Netscaler which in turn load-balances the requests to the new Exchange 2016 server

cas.domain.com points to the Exchange 2010 CAS server in site 1

cas1.domain.com points to the Exchange 2010 CAS/HT server in site 3. There are no mailboxes on the mbx server in site 3 (all migrated to the new Exchange 2016 server), so cas1.domain.com is never hit. All the Exchange servers in Site 3 are ready to be decommissioned. As a result, the mbx server in site2 can also be decommissioned.

So all client connections are effectively going through the new Exchange 2016 servers, albeit via the Netscaler first.

I have submitted a change request and will be applying the fix on the weekend. I will report back after this.

edit: The public facing DNS record for outlook.domain.com is also pointing to a Netscaler in site4, EAS has no such trouble proxying the connections to the Exchange 2010 CAS server in site1. EAS is working as expected.

The goal is to sort this issue out and then begin migrating all the users out of Site 1. Migration of users in Site 3 was a bit of a pilot. Users in site 3 (now in site 4 and on Exchange 2016) do not interact with mailboxes in Site 4, so this is not a problem for them. I don't want to migrate users to site 4, who will be still accessing exchange resources in site 1.